Fuel supply conrol system for internal combustion engine

Abstract

There is provided a fuel supply control system for an internal combustion engine, which is capable of controlling fuel cutoff according to an amount of oxygen stored in a catalytic converter to thereby enhance the purification rate of the catalytic converter while maintaining excellent fuel economy, thereby making it possible to improve exhaust emission characteristics. An amount of oxygen stored in the catalytic converter 13 arranged in an exhaust pipe 12 of an engine 3 is estimated (steps S 1 to S 29 ). A deceleration condition of the engine is detected (steps S 35, S 36 ). When the deceleration condition is detected, supply of fuel to the engine is cut off (step S 41 ). The cutoff of fuel supply is controlled based on the oxygen storage amount OSC (steps S 31, S 32, S 40, S 41 ).

What is claimed is:  
     
       1. A fuel supply control system for an internal combustion engine having an exhaust system, for controlling supply of fuel to said engine, comprising: 
       exhaust gas purification means arranged in said exhaust system of said engine;  
       oxygen storage amount estimation means for estimating an amount of oxygen stored in said exhaust gas purification means, as an oxygen storage amount;  
       deceleration condition-detecting means for detecting a deceleration condition of said engine;  
       fuel supply cutoff means for cutting off said supply of said fuel to said engine when said deceleration condition-detecting means has detected said deceleration condition; and  
       control means for controlling said fuel supply cutoff means based on said oxygen storage amount estimated by said oxygen storage amount estimation means.  
     
     
       2. A fuel supply control system according to  claim 1 , including fuel cutoff inhibition means for inhibiting said fuel supply cutoff means from cutting off said supply of said fuel to said engine, when said oxygen storage amount estimated by said oxygen storage amount estimation means is larger than a predetermined maximum storage amount. 
     
     
       3. A fuel supply control system according to  claim 1 , including delay time-setting means for setting a delay time over which execution of said cutoff of said supply of said fuel to said engine is delayed, according to said oxygen storage amount. 
     
     
       4. A fuel supply control system according to  claim 1 , including engine rotational speed-detecting means for detecting a rotational speed of said engine, and intake pipe absolute pressure-detecting means for detecting an intake pipe absolute pressure, and wherein said oxygen storage amount estimation means estimates said oxygen storage amount by adding or subtracting an incremental/decremental value calculated based on a space velocity representative of a volume of exhaust gases, to or from an immediately preceding value of said oxygen storage amount, in accordance with a state of fuel supply control, said space velocity being calculated by using a product of a value of said engine rotational speed detected by said engine rotational speed-detecting means and a value of said intake pipe absolute pressure detected by said intake pipe absolute pressure-detecting means.